I made a small list long while ago, but it still holds today

https://medium.com/@012parth/what-source-code-is-worth-study...

I dont think this is a good idea, actually. Good design is about making good trade offs at the right point in time.

A code base with excellent design will show you the end state but not how it got there but probably not the trade offs and decisions involved.

Practicing refactoring on subpar code bases and dealing with the consequences of your decisions is a better way to improve.

Your own. Everyone else's is trash. Never understand someone else's code-- the whole point is that there should be just a handful of functions of yours I can call, and shouldn't ever care to see how the sausage is made. Otherwise, your abstraction sucks

These are several years old at this point, but many open source project leaders contributed to the series "The Architecture of Open Source Applications", which is free to read online: https://aosabook.org/en/index.html

Trying to learn software design by looking at code is kind of like trying to learn about architecture looking at the bricks that make up a building.

To learn about design you need a wider perspective. You can theoretically learn it from code but it won’t be most effective. Look at great documentation and literature about design instead.

Maybe I’m just not good enough at paying attention, but for me it seems like you have to actually run into problems over and over and figure out how to avoid the problems. Then you end up being able to mentally simulate what problems you will run into, and design is basically all about avoiding future problems of various kinds (and balancing tradeoffs about which future problems to avoid and how much effort to put into each, whether you can solve multiple with one design play, etc).

What if the question is born out of the insight that his team's software is poorly designed, motivating the desire to get outside input?

What if the question is asked by a college student?

My immediate reaction to this question is: "your team's". Nothing will teach you more about how to design software then really understanding why good and bad solutions were adapted to solve a certain real problem.

Software exists precisely because there is still a messy layer connecting user requirements to actions on a computer. If there was not messiness then we could just automate it all. Approaching software from some sort of Platonic ideal of what software should be will frequently lead to bad decisions on it's own.

When you start to see how certain pressures lead to certain paths you learn to recognize the wrong decisions that are often good at the time, and avoid them. At the same time, you need to learn to develop methods that work quickly and effectively. By far the biggest real challenge in real world software is time constraints. This is almost never discussed in theoretical views of software, but the truth is you're always going to be writing code under pressure to ship. You will come across situations where you do not have time to do what you want to do or think is best.

Good software is software that runs and solves the user need, but you will come to realize that there are design solutions that will make successfully running happen more often. The best way to find these is to study the real software you're writing.